The present invention relates to a method of manufacturing a circuit element, and particularly, to a method of forming a fine structure element such as a single-electron tunneling element or the like.
In recent years, integration of various circuit elements including a semiconductor device has been promoted, accompanying downsizing of circuit patterns of LSI elements forming part of a circuit element. The downsizing of patterns not only has lead to narrowed wires of elements currently used, but also has required developments of circuit elements based on a new concept, since requisites for the operational principle of the concept cannot simply be achieved by downsizing.
As a countermeasure under consideration for responding to such a demand, a single-electron tunneling element has been proposed. A single-electron tunneling element forms a fine conductive material of 0.1 .mu.m or less which is separated by tunneling barriers and utilizes a characteristic that electrostatic energy per electron in the conductive material is sufficiently large. Therefore, it is necessary to form fine patterns with high accuracy. Particularly, in order to prepare such a single-electron tunneling element operational at a normal temperature that is effective in practical use, it is required to form a conductive material of a level of several tens nm or less. However, it is difficult for a normal lithography method to form such a fine pattern with sufficient accuracy of, e.g., .+-.10% or less with respect to a designed size, which is equivalent to a range of plus and minus several nm or less.
Conventionally, a processing mode of a scanning tunnel microscope (STM) is used to prepare such a fine pattern in many cases. Processing using the STM achieves only a very low throughput, and therefore, cannot be adopted in mass-production in the future. Meanwhile, it has been attempted to form a polycrystal narrow wire having a wire width of about 0.1 .mu.m or less by using a normal electron beam lithography method, and to obtain a desired characteristic by using connections at grain boundaries of polycrystal. However, there is a limit to artificial control of grain boundaries of polycrystal within the capacity of current techniques. It is therefore difficult to ensure uniformity over the entire surface of the substrate.
Thus, downsizing of elements has been accompanied by more and more difficulties in achieving both a high throughput and high accuracy. Not only in case of a single-electron tunneling element, but also in case of forming a fine pattern with a sufficient throughput and high accuracy, there is a problem that no effective method has been established.
The present invention has been made in view of the above situation and has an object of providing a method of manufacturing a circuit element, which is capable of forming a fine pattern with a useful throughput and useful accuracy, thereby to realize a fine circuit element such as a single-electron tunneling element or the like.